1. Field of the Invention
This invention relates to battery separators, and in particular relates to an improved dip process for forming a microporous separator envelope about a battery plate, such that the envelope functions as a battery separator for use in lead-acid batteries of the type, for example, used in automobiles.
2. Description of the Prior Art
In the prior art, it has been thought desirable to form a battery separator directly on a battery plate by a method of dipping the plate in one or more solutions. While many prior art patents speak of such a process, in fact few have achieved any commercial success.
To prevent the positive and negatively charged plates or electrodes of lead-acid batteries from coming into contact with each other, thereby self discharging the battery plate, sheets of separator material are positioned between the positive and negative battery plates. This separator material is usually comprised of preformed separator sheets which must be positioned either mechanically or manually between the positive and negative electrodes or sealed on three sides about one of the plate types, thereby enveloping it. In today's world of high speed mass production, these techniques are slow, labor intensive and most importantly generate large scrap rate losses when automated, and are inefficient processes for the manufacturer of batteries.
The present invention overcomes the necessity of enveloping the battery plates with separator material by mechanical process or positioning separator material between the plates. A separator envelope is produced by an improved dip process.
Prior patents have proposed methods of dipping or applying a coating on a battery plate. See the discussion in my prior U.S. Pat. No. 4,524,509 incorporated herein by reference. As discussed in detail in my prior U.S. Pat. No. 4,524,509, prior, proposed methods of producing a battery separator by dipping failed to produce a commercially acceptable battery separator material. In my prior U.S. Pat. No. 4,524,509, disclosed a method of enveloping a battery plate by a dip process which involved first removing air bubbles from the battery plate by dipping the plate in the first liquid, then dipping the plate into a polymer-solvent-filler suspension. After removal from the polymer-solvent-filler suspension, the plate was dried by evaporation or contacted with a nonsolvent and then dried. The result was the formation of a commercially acceptable microporous separator envelope about the battery plate.